The present invention relates to an X-ray CT system, gantry apparatus, console terminal, method of controlling them, an-d storage medium, for obtaining an X-ray tomographic image of a subject by X-ray irradiation.
An X-ray CT (computed tomography) system and apparatus comprises, in a broad classification, an apparatus of a toroidal shape having a cavity portion (generally referred to as a gantry apparatus), an operating console for supplying several types of control signals to the gantry apparatus and reconstructing an X-ray tomographic image based on signals (data) obtained from the gantry apparatus for display, and a carrier apparatus for supporting a subject (human subject) fixed within the cavity portion of the gantry apparatus and carrying the subject toward the cavity portion.
The gantry apparatus comprises a rotating section incorporating therein an X-ray generating source (X-ray tube) and a detecting section provided across the cavity portion for detecting X-rays emitted from the X-ray generator.
In performing a scan, the subject is laid on the carrier apparatus and conveyed toward the cavity portion of the gantry apparatus. Then, the rotating section of the gantry apparatus is driven to rotate and at the same time the X-ray tube is driven, thereby emitting X-rays from different directions toward the subject, and detecting X-rays having passed through the subject by the detecting section. The operating console receives signals corresponding to the intensity of the transmitted X-rays transferred from the gantry apparatus, and arithmetically produces an image corresponding to the X-ray attenuation factors in a cross-section of the subject based on the signals. The image reproduced is generally referred to as an X-ray tomographic image, and the processing to reproduce the X-ray tomographic image is referred to as reconstruction of an X-ray tomographic image, or simply as reconstruction. Each pixel constituting the reconstructed X-ray tomographic image is a numerical value representing the magnitude of the X-ray attenuation factor (or the X-ray transmission factor), which value is generally referred to as a CT number.
Thus, the X-ray CT system can scan several regions such as the head, thorax (lungs) or abdomen of a subject, and is effectively used for diagnosis.
Although in some cases an X-ray tomographic image can be obtained which is high in contrast and easy to use in diagnosis, in other cases an X-ray tomographic image which is low in contrast and difficult to use in diagnosis is obtained, depending upon the measured region of the subject. Simply stated, the contrast can be conveniently considered as being low when all the pixels constituting an X-ray tomographic image have almost the same CT numbers, and being high when the CT numbers are considerably different from one another.
Low contrast is often found in X-ray tomographic images of the head of the subject. The reason of this is that the head, i.e., the brain, is largely composed of white matter and gray matter, resulting in almost identical CT numbers. On the other hand, an X-ray tomographic image of the abdomen has high contrast, and an image which is easy to use in diagnosis can be easily obtained.
The present invention was made to address such a problem, and is directed to providing an X-ray CT system, gantry apparatus, operating console and storage medium which enable an X-ray tomographic image to be obtained with high quality while minimizing the exposed dose to a subject by employing the most suitable filter according to the region of the subject to be scanned.
In order to solve such a problem, a gantry apparatus in an X-ray CT system of the present invention comprises, for example, a configuration as described below.
Specifically, there is provided a gantry apparatus in an X-ray CT system equipped with a gantry rotating section having an X-ray generating source and an X-ray detecting section for detecting X-rays emitted from the X-ray generating source across a cavity portion for positioning a subject, which gantry apparatus comprises a plurality of filters having different X-ray transmission properties, and positioning means for, when one of the plurality of filters is selected, positioning the selected filter at a position between the X-ray generating source and the X-ray detecting section in the proximity of the X-ray generating source.
According to a preferred embodiment of the present invention, the plurality of filters are provided in a single filter unit.
Moreover, the positioning means is preferably means for controlling a motor for moving the filter unit.
Moreover, the plurality of filters preferably include a first filter for scanning the head of the subject and a second filter for scanning the abdomen, and when the X-ray transmission factors of the first and second filters are represented as F1 and F2, respectively, the following relationship preferably holds:
F2 less than F1.
Furthermore, the plurality of filters preferably further include a third filter for use in scanning the thorax having an X-ray transmission factor of F3, and the following relationship holds:
F3 less than F2 less than F1.
Further, the thicknesses of the plurality of filters are preferably different.
Moreover, the gantry apparatus comprises means for connecting an operating console that supplies an instruction signal to the gantry apparatus and performs reconstruction processing for an X-ray tomographic image based on data transferred from the gantry apparatus, and the motor control means controls the motor according to instruction commands from the operating console.
The present invention also provides a method of controlling a gantry apparatus. Specifically, it provides a method of controlling a gantry apparatus in an X-ray CT system equipped with a gantry rotating section having an X-ray generating source and an X-ray detecting section for detecting X-rays emitted from the X-ray generating source across a cavity portion for positioning a subject, which method comprises a step of providing a plurality of filters having different X-ray transmission properties, and a positioning step of, when one of the plurality of filters is selected, positioning the selected filter at a position between the X-ray generating source and the X-ray detecting section in the proximity of the X-ray generating source.
In this method, the plurality of filters are preferably provided in a single filter unit.
Moreover, the positioning step is preferably a step of controlling a motor for moving the filter unit.
According to a preferred embodiment of the present invention, it is also an object thereof to provide an operating console connected to the above-described gantry apparatus.
The operating console is connected to the aforementioned gantry apparatus, supplies an instruction signal to the gantry apparatus and performs reconstruction processing for an X-ray tomographic image based on data transferred from the gantry apparatus, and the operating console comprises display means for displaying a menu for selecting a scan region of a subject, decision means for deciding which of the plurality of filters is to be employed based on the selected scan region, and means for supplying an instruction indicating the filter selection decided by the deciding means to the gantry apparatus.
According to a preferred embodiment of the present invention, the operating console comprises storage means for storing respective correction data corresponding to the plurality of filters incorporated in the gantry apparatus, and correction means for correcting data representing the result of a scan transferred from the gantry apparatus using correction data corresponding to the filter decided by the deciding means, and reconstructs an X-ray tomographic image using data corrected by the correction means.
Preferably, the display means further displays at least one field for inputting the size of the subject, and the deciding means decides a filter to be employed based on the input subject size and scan region.
The present invention also provides a method of controlling an operating console. Specifically, it provides a method of controlling an operating console that supplies an instruction signal to the aforementioned gantry apparatus and performs reconstruction processing for an X-ray tomographic image based on data transferred from the gantry apparatus, which method comprises a display step of displaying a menu for selecting a scan region of a subject, a decision step of deciding which of the plurality of filters is to be employed based on the selected scan region, and a step of supplying an instruction indicating the filter selection decided at the deciding step to the gantry apparatus.
Moreover, the present invention provides a storage medium for storing a program code for an operating console. Specifically, it provides a storage medium for storing a program code for an operating console that supplies an instruction signal to the aforementioned gantry apparatus and performs reconstruction processing for an X-ray tomographic image based on data transferred from the gantry apparatus, which storage medium stores a program code of a display step of displaying a menu for selecting a scan region of a subject, a program code of a decision step of deciding which of the plurality of filters is to be employed based on the selected scan region, and a program code of a step of supplying an instruction indicating the filter selection decided at the deciding step to the gantry apparatus.
Furthermore, the present invention provides an X-ray CT system. Specifically, it provides an X-ray CT system equipped with a gantry apparatus and an operating console, the gantry apparatus having an X-ray generating source and an X-ray detecting section for detecting X-rays emitted from the X-ray generating source across a cavity portion for positioning a subject, and the operating console supplying an instruction signal to the gantry apparatus and performing reconstruction processing for an X-ray tomographic image based on data transferred from the gantry apparatus, which gantry apparatus comprises a plurality of filters having different X-ray transmission properties, and positioning means for, when one of the plurality of filters is selected, positioning the selected filter at a position between the X-ray generating source and the X-ray detecting section in the proximity of the X-ray tube, and which operating console comprises display means for displaying X-ray generating source for selecting a scan region of a subject, decision means for deciding which of the plurality of filters is to be employed based on the selected scan region, and means for supplying an instruction indicating the filter selection decided by the deciding means to the gantry apparatus.
Preferably, the operating console further comprises storage means for storing respective correction data corresponding to the plurality of filters incorporated in the gantry apparatus and correction means for correcting data representing the result of a scan transferred from the gantry apparatus using correction data corresponding to the filter decided by the deciding means, and the operating console reconstructs an X-ray tomographic image using data corrected by the correction means.
Moreover, the display means preferably further displays at least one field for inputting the size of the subject, and the deciding means decides a filter to be employed based on the input subject size and scan region.
Moreover, the plurality of filters are preferably provided in a single filter unit.
Further, the positioning means is preferably means for controlling a motor for moving the filter unit.
Moreover, the plurality of filters preferably include a first filter for scanning the head of the subject and a second filter for scanning the abdomen, and when the X-ray transmission factors of the first and second filters are represented as F1 and F2, respectively, the following relationship holds:
F2 less than F1.
Moreover, the plurality of filters preferably further include a third filter for use in scanning the thorax, having an X-ray transmission factor of F3, and the following relationship holds:
F3 less than F2 less than F1.
Moreover, the thicknesses of the plurality of filters are preferably different.
Moreover, the display means preferably further displays at least one field for inputting the size of the subject, and the deciding means decides a filter to be employed based on the input subject size and scan region.
According to the present invention as described above, an X-ray tomographic image can be obtained with high quality while minimizing the exposed dose to a subject by employing the most suitable filter according to the region of the subject to be scanned.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.